Murine gammaherpesvirus infection is skewed toward Igλ+ B cells expressing a specific heavy chain V-segment

Abstract

One of the defining characteristics of the B cell receptor (BCR) is the extensive diversity in the repertoire of immunoglobulin genes that make up the BCR, resulting in broad range of specificity. Gammaherpesviruses are B lymphotropic viruses that establish life-long infection in B cells, and although the B cell receptor plays a central role in B cell biology, very little is known about the immunoglobulin repertoire of gammaherpesvirus infected cells. To begin to characterize the Ig genes expressed by murine gammaherpesvirus 68 (MHV68) infected cells, we utilized single cell sorting to sequence and clone the Ig variable regions of infected germinal center (GC) B cells and plasma cells. We show that MHV68 infection is biased towards cells that express the Igλ light chain along with a single heavy chain variable gene, IGHV10-1*01. This population arises through clonal expansion but is not viral antigen specific. Furthermore, we show that class-switching in MHV68 infected cells differs from that of uninfected cells. Fewer infected GC B cells are class-switched compared to uninfected GC B cells, while more infected plasma cells are class-switched compared to uninfected plasma cells. Additionally, although they are germinal center derived, the majority of class switched plasma cells display no somatic hypermutation regardless of infection status. Taken together, these data indicate that selection of infected B cells with a specific BCR, as well as virus mediated manipulation of class switching and somatic hypermutation, are critical aspects in establishing life-long gammaherpesvirus infection.

Dangerous Liaisons: Gammaherpesvirus Subversion of the Immunoglobulin Repertoire

“…This suggests that KSHV might edit the BCR in the peripheral lymphoid tissues and lead to some potential autoreactive or non-functional B cells outside of the bone marrow. As detailed and discussed below, Igκ light chain bias was also recently reported by us [ 88 ] and Collins et al [ 89 ] for MHV68-infected B cells from mice at the peak of latency in the spleen. It is unclear by what mechanism KSHV drives receptor editing and for what purpose this might serve the virus in the host.…”

“…Two recent studies used a traceable MHV68 infection mouse model to analyze the Ig repertoire of infected cells [ 88 , 89 ]. A transgenic virus which expresses histone H2B fused to EYFP fluorescent protein (MHV68-H2BYFP) [ 158 ] was used to infect mice and isolate MHV68+ B cells.…”

“…Significantly, in the MHV68+ population, Ighv10-1 was highly utilized (~20% of all MHV68+ B cells), with little representation of Ighv1-82 in the MHV68+ population. The bias for Ighv10-1 was not only observed recurrently within individual mice, but also spanned three individual mouse facilities [ 88 , 89 ]. Furthermore, Collins et al [ 89 ] examined MHV68+ plasma cells, observing the biased Ig repertoire and prominent Ighv10-1 utilization.…”

“…The bias for Ighv10-1 was not only observed recurrently within individual mice, but also spanned three individual mouse facilities [ 88 , 89 ]. Furthermore, Collins et al [ 89 ] examined MHV68+ plasma cells, observing the biased Ig repertoire and prominent Ighv10-1 utilization. Mouse Ighv10-1 together with closely related Ighv10-3 are sole members of Ighv10 family in the C57Bl/6 strain.…”

“…The GC reaction is normally driven by BCR antigen affinity and Tfh signals. The SHM in MHV68+ cells did not display a physiologically relevant difference between MHV68+ and MHV68- populations [ 88 , 89 ]. Mutation location was significantly biased towards the antigen-binding CDR loops, an indication of antigen selection, since mutations are randomly generated, but clones with improved affinity were antigen selected [ 88 ].…”